Tin pot



May 30, 195o H. c. MQRROW 2,509,515

TIN POT Filed Deo. 24, 1947 lnvmzor: #4H/67V C Ame/90W,

Patented May 30, 1950 TIN POT Harry C. Morrow, Gary, Ind., assignor to Carnegie-Illinois Steel Corporation, a corporation of New Jersey Application December 24, 1947, Serial No. 793,705

7 Claims.

This invention relates to hot-dip tin coating and more particularly to improved means for ad- Justing the temperature of the outlet portion of hot-dip tin coating pots.

In hot-dip tin coating. ferrous base metal in strip or sheet form is passed through the entry side of the tin pot which contains the molten tin and exits upwardly through a Ibath of oil-like material, such as palm oil, to prevent oxidation of the molten tin and also too hasty chilling of the coating. Normally, the molten tin is maintained at a temperature of about 625 to 640 F. and the oil bath which floats on the tin at about 460 to 465 F. Due to continuous feeding of strip metal or successive sheets through the tin pot, a certain amount of oil is carried off by the coated metal thereby lowering the oil level. Also passage of the tinned metal from the higher temperature molten tin bath through the oil bath raises the temperature of the oil bath. It is therefore necessary to periodically add cooled oil to the oil bath to maintain the temperature and the upper level at the4 desired point. When the cooling oil is added, it gravitates to the bottom of the pot and then rises along the path of sheet or strip travel causing unequal temperatures inthe oil bath. By ac- Y tual check it has been determined that the temperature of the oil bath may vary as much as 35, which results in cold spots and freezing of the coating. Such spots cause defects in the coating necessitating rejection thereof.

It is accordingly an object of the present invention to provide a tin pot having means for adding cooled oil to the oil bath without causing uneven temperatures therein.

It is a further object to provide heat exchanger means for the oil bath on the exit side of hotdip tin pots.

It is still another object to provide a heat exchanger in the oil bath at the outlet side of hotdip tin pots which is simple in design and at the same time eflicient in operation.

The foregoing and further objects will become apparent from the following specication when read in conjunction with the attached drawings, wherein:

Figure 1 is a longitudinal vertical section of a hot-dip tin pot embodying the heat exchanger of my invention; 4

Figure 2 is an enlarged vertical sectional elevation of the heat exchanger; and

Figure 3 is a perspective view of the Aheat exchanger.

Referring more particularly to the drawings, the numeral 2 designates a conventional'hot-dip tin pot having an entry side l containing molten tin and an exit side G containing exit rolls 8 and an oil-likebath i0. The molten tin is maintained at a level I2 below the exit rolls 8 and the bath I0 is maintained at a level I4 above the top of the rolls 8. Means such as rolls I6 and deilector I8 may be provided for passing the sheets or strip through the molten tin and guiding them upwardly to the exit rolls 8.

In accordance with the teachings of my invention, there is disposed in the oil bath I 0, a narrow, rectangular open or closed bottom, boxlike, sheet-metal heat exchanger 20 which is mounted on suitable brackets 22 so that the top 24 thereof is disposed below the oil bath level I4. The length of the heat exchanger is such that it extends at least half way across the outlet portion and preferably is about 3/5 to 1% of the width thereof. This permits the bath to iiow therearound due to convection currents and currents induced by the passage of coated metal through the bath. The front face 26 of the heat exchanger, which faces the exit rolls 8, has its upper edge cut away as at 28 so that it is slightly lower than the top of the back and side faces. In addition, this front face 2E`is preferably formed of sheet metal having a thinner cross-section than that of the back and sides so as to provide greater heat conductivity on the side facing the path of ow of the exiting coated metal. The heat exchanging characteristics of this face may be further improved by wholly or partially corrugating it as shown at 30. The lower portion of the back face of the heat exchanger may be slanted as at 32 to provide a narrow bottom portion 34. a part of which ex-i tends into the molten tin, thus sealing ofi the surrounding hot oil. `A pipe 36 extends downwardly inside of the heat exchanger along the midportion of the back wall thereof to a point about mid-way relative to the height of the heat exchanger. Oil, which is cooled to the desired temperature, is forced through the pipe 36 into the heat exchanger and flows downwardly towards the bottom of the heat exchanger and up wardly along the front face thereof before flowing into the oil bath over the shorter front face 26.

By so introducing the cooled oil through the heat exchanger of my invention, it is prevented from mixing immediately with the hot oil in the exit compartment. The cooled oil upon being fed into the heat exchanger flows down- Iwardly therein until the feeding pressure is exhausted and reverses its direction of now rising upwardly along the front face of the heat exchanger. In so doing, the temperature of the oil flowing through the heat exchanger tends to become equalized with that in the exit compartment of the tinrpot before it flows over-the top edge of the front face thereof. It has been demonstrated in commercial operating conditions that by using the heat exchanger of this invention in the manner above described, that varispots in the oil bath and eliminates uneven freezing of the coating hereinbei'ore described. Moreover it results in greatly improved peraeoacns vformance of the tin pot in addition to the improved quality of the product.

embodiment of my invention, it will be understood that this embodiment is merely for the purpose of illustration and description and that various other forms may be devised within the scope of my invention, as defined in the appended claims.

I claim:

1. In a pot for coating base metal with a coating of molten metal comprising an inlet portion adapted to contain'the molten metal and an outlet portion adapted to contain an oil-like bath floating on the molten metal, the improvement consisting of a heat exchanger disposed in the said outlet portion and adapted to be contacted by the oil-like bath therein, said heat exchanger comprising a vertically disposed narrow box-like container having the top of the front face thereof at a lower elevation than the back and side faces and means for flowing oil-like material through said heat exchanger prior to its admission to the bath.

2. In a pot for coating base metal with a coating of molten metal comprising an inlet portion adapted to contain the molten metal and an outlet portion adapted to contain an oil-like bath floating on the molten metal, the improvement consisting of a heat exchanger disposed in the said outlet portion and adapted to be submerged in the oil-like bath therein, said heat exchanger comprising a narrow box-like container having its front wall facing the outlet path of the coated metal therethrough, the top of said wall beine,r at a lower elevation than the side and back walls, said front face having a thinner cross-section than the back and side walls and means for flowing oil-like material through said heat exchanger prior to its admission to the bath.

3. In a pot for coating base metal with a coating of molten metal comprising an inlet portion adapted to contain the molten metal and an outlet portion adapted to contain an oil-like bath floating on the molten metal, the improvement consisting of a heat exchanger disposed in the said outlet portion and adapted to be submerged in the oil-like bath therein, said heat exchanger comprising a narrow box-like container having its front wall facing the outlet path of the coated metal therethrough, said front wall being corrugated and means for flowing oil-like material through said heat exchanger prior to its admission to the bath.

4. In a pot for coating base metal with a coating of molten metal comprising an inlet portion adapted to contain the molten metal and an outlet portion adapted to contain an oil-like bath floating on the molten metal, the improvement consisting of a heat exchanger disposed in the said outlet portion and adapted to be submerged in the oil-like bath therein, said heat exchanger comprising a narrow box-like container having its front wall facing the outlet path of the coated metal therethrough, said front wall being corrugated and having a thinner cross-section than thel back andside walk and means for owing oil-like material *throughl said heatexchanger prior to its admimion to the batirv 5. In a pot for coating base metalwith a coatin-g of molten metal comprising an inlet portion adapted to contain the molten metal and-.an outlet portion adapted to contain an oil bath floating on the molten'metal. the improvement consisting .of a heat exchanger disposed in the outlet portion and adapted to be submerged in the oil bath therein with its lower edge disposedin the molten coating metal, said heat exchanger comprising a, narrow box-like container having its front wall facing the outlet path of the coated metal therethrough, said front wall being corrugated and having a thinner cross-section than the back and side walls, the top of said front wall being lower than the back and side walls and means for flowing oil through said heat exchanger prior to its admission to the bath.

6. In a pot for coating base metal with a coating of molten metal comprising an inlet portion adapted to contain the molten metal and an outlet portion adapted to contain an oil-like bath floating on the molten metal through which the base metal is adapted to be drawn in an upward direction, the improvement consisting of a heat exchanger disposed in the said outlet portion and adapted to be contacted by the oil-like bath therein, said heat exchanger comprising a boxlik e container disposed at one side of the path of travel of the coated metal and having its front face substantially parallel thereto, and a pipe disposed closer to the back wall than the front wall of said box-like container extending downwardly to the mid-portion thereof for admitting cooling oil-like material under pressure into said heat exchanger, whereby the oil-like material admitted to said container flows downwardly and upwardly therethrough prior to its entry into the oil-like bath.

7. In a pot for coating base metal with a coating of molten metal comprising an inlet portion adapted to contain the molten metal and an outlet portion adapted to contain an oil-like bath floating on the molten metal through which the base metal is adapted to be drawn in an upward direction, the improvement consisting of a heat exchanger disposed in the said outlet portion and adapted to be contacted by thev oil-like bath therein, said heat exchanger comprising a boxlike container disposed at one side of the path of travel of the coated metal and having its front face substantially parallel thereto, and a downwardly extending pipe disposed in said boxlike container adjacent the rear face thereof for admitting cooling oil-like material thereto under pressure, whereby the oil-like material admitted to said container flows downwardly toward the bottom thereof and upwardly along the front face thereof prior to its entry into the oil-like bath.

HARRY C. MORROW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

